An Internationalized Domain Name in Applications (IDNA) is an
industry standard for encoding Internet Domain Names that contain in
whole or in part, in a language-specific script or alphabet,
such as Arabic, Chinese, Cyrillic, Tamil, Hebrew or the Latin
alphabet-based characters with diacritics or ligatures, such as
French. These writing systems are encoded by computers in
multi-byte Unicode. Internationalized domain names are stored
in the Domain Name System as ASCII strings using Punycode
transcription.

keep-alive

A technique for communicating between HTTP client and server
when connection is not closed after sending response but kept
open for sending next request through the same socket.

It makes communication faster by getting rid of connection
establishment for every request.

nginx

Nginx [engine x] is an HTTP and reverse proxy server, a mail
proxy server, and a generic TCP/UDP proxy server.